Take this for what it is worth:

North Korean leader Kim Jong-il’s son and rumored heir apparent on Sept. 9 visited the Ninth North Korean Army Corps in Chongjin, North Hamgyong Province which is in charge of guarding the North Korea-China border. The visit to the corps’ commander and political commissars was conducted in tight secrecy and came amid growing fears about discipline at the unit.

Kim Jong-un reportedly said, “The military unit which the general [Kim Jong-il] considers the most important is the Ninth Army Corps in charge of guarding the border.”

An inside source in North Korea said the first frontline for North Korea is not the military demarcation line between the two Koreas but the North Korea-China border. The atmosphere there is so tense that the sound of North Korean soldiers shooting at defectors is heard almost every day.  [Chosun Ilbo]

Read the rest at the link, but as always it is impossible to confirm accounts like this, but the statement that the Chinese border is the real frontline for the North Korean regime is true considering the thousands of defectors moving across the border every year.  These defections this year has received increased media attention due to the Ling/Lee detainment issue.  As usual with North Korean human rights issues this recent focus on North korean abuses is quickly dissappearing back down the memory hole.